1. Field of the Invention
This invention relates to abrasive articles, in particular abrasive articles that comprise a plurality of abrasive particles and a plurality of erodible grinding aid agglomerates.
2. Discussion of the Art
Abrasive articles generally comprise abrasive grains secured within a binder. In a bonded abrasive, the binder bonds the abrasive grains together in a shaped mass. Typically, this shaped mass is in the form of a wheel and thus it is commonly referred to as a grinding wheel. In nonwoven abrasives, the binder bonds the abrasive grains to a lofty, open, fibrous substrate. In coated abrasives, the binder bonds the abrasive grains to a substrate or backing. Coated abrasives may include a first coated layer bonded to one side of the backing (commonly referred to as a make coating), at least one layer of abrasive grains bonded to the backing by the make coating, and a second coating layer overlaying the abrasive particles. The second coating layer commonly is referred to as a size coating; it reinforces the retention of the abrasive particles. Coated abrasives also may include an additional "supersize" coating overlaying the size coating.
Abrasive binders typically consist of a glutinous or resinous adhesive, and, optionally, additional ingredients. Examples of resinous adhesives include phenolic resins, epoxy resins, urethane resins, acrylate resins and urea-formaldehyde resins. Examples of typical additives include grinding aids, fillers, wetting agents, surfactants, pigments, coupling agents, and dyes.
The addition of grinding aids can significantly affect the chemical and physical processes of abrading metals to bring about improved performance. It is believed that grinding aids either (1) decrease the friction between the abrasive grains and the workpiece being abraded, (2) prevent the abrasive grains from "capping", i.e., prevent metal particles from becoming welded to the tops of the abrasive grains, (3) decrease the interface temperature between the abrasive grains and the workpiece, and/or (4) decrease the required grinding force. In certain grinding aid applications, such as grinding stainless steel, grinding aids significantly improve the performance of the abrasive article.
The abrasive industry is always evaluating means to improve the abrading efficiency of abrasive articles without unduly increasing their cost. It is desired to provide a means for utilizing a high concentration of grinding aid in an abrasive product without significantly reducing the strength of the binder.